Fundamental Physics from the Sky

Transcription

1 Fundamental Physics from the Sky Based on: SP, (PRD) Kamionkowski & SP, (PRL) Jeltema & SP, (JCAP) Jeltema & SP, (ApJ) SP, (PRD) Colafrancesco, SP & Ullio, astro-ph/ (PRD) and (A&A) Ohio State University Tuesday, April 7, 2009

2 What is the fundamental particle physics nature of Dark Matter? More than 4 in 5 grams of matter are Dark! Keith Olive & Stefano Profumo (co-leaders), DUSEL Theory White Paper Dark Matter

3 From the particle point of view, DM is new physics A natural place where to expect New Physics: Electro-Weak Scale Hierarchy problem stability of the EW scale to radiative corrections Gauge Coupling Unification Directly and accurately probed with colliders WIMP miracle tantalizing connection between DM and the EW scale

4 A WIMP Miracle Ω χ h cm 3 /s Ω CDM h σ χχ anything v rel Standard Thermal Freeze-out If χ is weakly interacting (~neutrino), and has EW mass, then σ χχ anything G 2 2 F m χ (# ) π (# ) cm 2 v rel c σ χχ anything v rel (# ) cm 3 /s Lee and Weinberg (1977); Vysotsky, Dolgov and Zeldovich (1977)

5 WIMPs can be detected! Correct Relic Density Efficient Annihilation in the Early Universe (Indirect Detection) Efficient Annihilation Now χ q χ q (Particle Colliders) Efficient Producrtion Now Efficient Scattering Now (Direct Detection) slide concept credit: J. Feng

6 WIMPs pair-annihilate to stable, SM particles Indirect Dark Matter Detection Can we do fundamental physics with indirect DM detection? Synchrotron Radio X-ray Gamma Rays Gamma Ray Antimatter

7 arxiv:

8 arxiv:

9 HEAT AMS (With Solar Modulation) Emulsion Chambers Nature, Nov 2008

10 New Physics Interpretations of PAMELA and ATIC: galactic DM annihilates and produces high energy e+e- Is this out of necessity? Or are we upsetting (grumpy) William of Occam? Not only do (several classes of) astrophysical Entia non sunt sources perfectly well explain all data: multiplicanda Sources that explain the data (e.g. pulsars) exist, are observed, and have names præter (e.g. Geminga, from the milanese dialect necessitatem no ghe minga, it s not there, William of Occam the first UnID GR source, radio quiet)

11 Pulsars seed e+e- direct pair production (strong rotationally induced electric fields in the magnetoshpere accelerate and extract e- from stellar surface, which radiate gamma rays; gammas cascade produce e+e- pairs, escaping the magnetosphere from the polar cap regions) SNR & PWN shock acceleration

12 Propagation of charged species: diffusion equation Distribution function 0: Coulomb; 1: Brems; 2: IC & Synch

13 Approximate solution to the electron/positron distribution function (*) (only IC and Synch losses) (*) Atoyan, Aharonian, Volk, 1995

14 Main feature of high-energy ( GeV) e + e - : they lose energy very efficiently Energy losses ~ E 2, via synchrotron and inverse Compton t Lifetime yr 1 TeV E B 5 µg 2 w ev/cm 3 1 In conjunction with conventional diffusion models, this short radiative cooling time limits the sources of high energy electron/positron both in space and time dist max D 0 t pc [ D cm 2 /s] Astrophysical sources relevant for energetic e+e- production must be young (~10 5 yr) and nearby (<kpc)

15 An asset of the pulsar scenario: pulsars exist, detailed catalogues, very accurate data

16 Examples of expected positron contributions from a few nearby pulsars and SNR Profumo,

17 Profumo, Same, for the total e + e - flux

18 ATIC and PAMELA data favor selected age / distance pulsar ranges: those favored ranges are populated by existing objects (from ATNF catalogue)

19 Conclusive results on the e + e - spectrum (orders of magnitude better than ATIC) will be presented soon by the Fermi Collaboration (S. Profumo talk on data interpretation, May APS Meeting)

20 Fermi discoveries of new gamma-ray pulsars will also play a decisive role! Fermi-LAT Pulsar Blind search at UC Santa Cruz (including the slug pulsar)) Profumo,

21 Role of Fermi: 1) Detailed spectrum (probably not sufficient to discriminate e+e- source (*) ) 2) More precise understanding of gamma-ray pulsars, new pulsars discoveries, IC emission from e+e- 3) More stringent constraints on DM (e.g. nearby clumps gamma-ray constraints (*) ) 4) Anisotropy 600 GeV if a single source is responsible for the Pamela positron fraction, most likely direction: Monogem) (*): Brun, Delahaye, Diemand, Profumo and Salati, arxiv:

22 Back to the Dark Matter Interpretation of the e+e- anomalies: 1) probably not necessary 2) conflicts with antiprotons concoct ways to suppress them 3) requires large boost factor One way out of (3), and interesting phenomenology anyways: Sommerfeld 1/v enhancement (e.g. heavy SUSY, secluded DM) (long range forces form bound states in the non-rel limit) σ v ~ 3 x cm 3 /s σ 26 (c / v) Right Relic Abundance (v ~ c/2 at freeze-out) ~10 3 Enhancement Today (v ~ 150 km/s) What happens when v 0 (M DM 0)?!

23 After chemical decoupling ( freeze-out ), WIMPs kinematically decouple at T~T kd from the relativistic thermal bath, and protohalos start to collapse Diemand et al, astro-ph/

24 Velocity Dispersion: Size : Dynamical Time: Kamionkowski & Profumo, [astro-ph], PRL 2009

25 WIMP annihilation rate in the first collapsed halos: where accounts for clumpiness Fraction of Dark Matter particles annihilating in the first halos: f<<1 already provide constraints (we want DM today, and CMB implies a matter density at recombination within 10% of its value today ) Kamionkowski & Profumo, [astro-ph], PRL 2009

26 Two astrophysical constraints from annihilation in the first protohalos: Diffuse radiation Background IGM Heating and Ionization outside transparency window [CMB distorsions from reionization e-] Diffuse Radiation Background Limit IGM Heating and Ionization Limit Kamionkowski & Profumo, [astro-ph], PRL 2009

27 1/v models must be tuned to avoid one or the other constraint by ~ 5-7 order of magnitude If a sufficiently suppressed 1/v contribution exists, then a violent burst of annihilation in the dark ages: we might detect it with Fermi! Back to standard scenario: what can we learn on the particle nature of dark matter from gamma-ray observations?

28 Where should we look for dark matter annihilation with Fermi? Which particle dark matter properties can we hope to learn about? Madau et al, (2006)

29 Assess which Dark Matter particle properties can be deduced with gamma-ray spectral analyses, and associated theoretical systematics Jeltema & Profumo, [astro-ph], JCAP 2008; DMFIT is publicly available

30 Fermi Science Tools simulation of the gamma-ray sky in the GC region 15 GeV Jeltema & Profumo, [astro-ph], JCAP 2008

31 Particle Dark Matter: msugra Benchmark Neutralino Models Focus Point Region (pair ann. in W+W-) Coannihilation region (light, quark-antiquark and τ+τ-) Bulk region (low mass, quark-antiquark) M. Battaglia et al, Eur. Phys. J. C22 (2001)

32 Use XSPEC to fit background and Dark Matter signal with DMFIT BCKG only BCKG+DM Dark Matter Broken Power-Law plus exp cutoff Jeltema & Profumo, [astro-ph], JCAP 2008

33 Mass & Annihilation Rate estimates, for a bright DM source at the GC with and without best fit to background alone, assuming bb final state 68, 90, 99% CL Dark Matter model C has a significant (15%) τ + τ - component This causes a bias in the mass extraction towards larger values! Jeltema & Profumo, [astro-ph], JCAP 2008

34 Similar approach, but studying the relative branching ratio contribution With background under control, DMFIT pins down the existence of a second (15%) annihilation mode is pinned down at the 99% CL! Including a second annihilation channel, the artificial bias in the mass disappears Jeltema & Profumo, [astro-ph], JCAP 2008

35 Fermi-LAT Sky after 4 days [Simulated] DM sky (Diemand et al) Despite great angular resolution, we expect several 100 s of unidentified sources!! Will be able to conclusively state that an unidentified source is associated to Dark Matter annihilation? One handle: look beyond gamma rays into other wavelengths!

36 χ χ π π 0 γ γ χ γ χ π decays from the hadronization of quark-antiquark, W + W - final states Prompt lepton pair production DM annihilations produce Gamma Rays as well as energetic electrons/positrons, with peculiar injection spectra

37 Electrons and Positrons diffuse and loose energy Inverse Compton off CMB and starlight photons, Bremsstrahlung and Synchrotron emission produce radiation from radio to gamma-ray frequencies 1. Source Term 2. Transport Equation 3. Compute the Signals (IC off CMB/starlight, Synchrotron emission, )

38 The multi-wavelength spectrum expected from a 41 GeV bino annihilating in the Coma cluster Colafrancesco, Profumo & Ullio, astro-ph/ , A&A 2005

39 Hard X-ray emission: generic feature of DM multi-wavelength spectra [Significant differences at lower/higher energies] Fit the Hard X-ray emission from the Ophiuchus Cluster with Dark Matter Compatible with EGRET limit on gamma ray emission (no detection from Oph.) Thermal Bremsstr. Dark Matter Profumo, [astro-ph], PRD 2008

40 Fermi-LAT will conclusively test this scenario! Radio follow-ups also crucial! Carried out with GMRT and VLA (Sanchez-Conde, Profumo et al, MNRAS 2009) Profumo, [astro-ph], PRD 2008

41 New Radio Telescopes (GMRT, VLA), much better angular resolution Only Diffuse Radio Emission: mini-halo at 1400 MHz (VLA) [Most likely NOT Dark Matter] Govoni et al, 2009 Perez-Torres, Zandanel Guerrero, Pal, Profumo, Prada and Panessa, arxiv: [astro-ph], MNRAS 2009

42 Radio observations are complementary to gamma-rays for indirect dark matter detection! Perez-Torres, Zandanel Guerrero, Pal, Profumo, Prada and Panessa, arxiv: [astro-ph], MNRAS 2009

43 Down-side: Clusters host other sources of non-thermal activity! Ideal environment for a multi-wavelength Dark Matter search campaign: Nearby Dwarf Galaxies ~10 ksec ~20 ksec Image credit: Marla Geha ~70 ksec

44 X-ray constraints are entirely complementary to gamma-ray! IXO 100 ksec Fermi 5yr Jeltema & Profumo, [astro-ph], ApJ 2008

45 NEW PHYSICS IN THE SKY: KEEP OCCAM IN MIND! Fundamental Physics can be explored with astronomical and/or astro-particle data, but it should be done only out of necessity GAMMA RAYS AND THE DARK MATTER ANNIHILATION RATE: Modifications to the Annihilation Cross Section (e.g. ~1/v) are strongly constrained by diffuse radiation from the first protohalos GAMMA RAYS AND DARK MATTER MASS/ANNIHILATION MODES: Gamma-Ray spectra (and fits to them) can yield important information on the fundamental nature of dark matter (e.g. annihilation modes, mass) GAMMA RAYS AND OTHER WAVELENGTHS: Gamma-Ray Indirect searches for dark matter annihilation are boosted and complemented by multi-wavelength observational campaigns

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